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Project: Ghana Emergency Medicine Collaborative

Document Title: Pulmonary Embolism Part 2 (2012)

Author(s): Rockefeller A. Oteng, M.D., University of Michigan

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Pulmonary Embolism Part 2

Rockefeller A. OtengGhana Emergency Medicine

Collaborative

Diagnostic EvaluationWells Clinical Prediction Rule for Pulmonary Embolism (PE)

• Clinical feature Points• Clinical symptoms of DVT 3• Other diagnosis less likely than PE 3• Heart rate greater than 100 beats per minute 1.5• Immobilization or surgery within past 4 weeks 1.5• Previous DVT or PE 1.5• Hemoptysis 1• Malignancy 1• Total points• • PE = pulmonary embolism; DVT = deep venous thrombosis.• Risk score interpretation (probability of PE):

>6 points: high risk (78.4%); 2 to 6 points: moderate risk (27.8%);

<2 points: low risk (3.4%)

Diagnostic EvaluationWells Clinical Prediction Rule for Deep Venous Thrombosis (DVT) Clinical feature Points

Active cancer (treatment within 6 months, or palliation)

1

Paralysis, paresis, or immobilization of lower extremity

1

Bedridden for more than 3 days because of surgery (within 4 weeks)

1

Localized tenderness along distribution of deep veins

1

Entire leg swollen  1

Unilateral calf swelling of greater than 3 cm (below tibial tuberosity)

1

Unilateral pitting edema 1

Collateral superficial veins 1

Alternative diagnosis as likely as or more likely than DVT

-2

Total points  

DVT = deep venous thrombosis.Risk score interpretation (probability of DVT): >/=3 points: high risk (75%); 1 to 2 points: moderate risk (17%); <1 point: low risk (3%).

Diagnostic Evaluation

• Laboratory:– Routine laboratory findings are nonspecific. – Include leukocytosis– Increased erythrocyte sedimentation rate (ESR),

and an elevated serum LDH or AST (SGOT)– normal serum bilirubin.

Diagnostic Evaluation

• Arterial blood gas– Arterial blood gas (ABG) measurements and pulse

oximetry have a limited role in diagnosing PE. – ABGs usually reveal hypoxemia

• Hypocapnia,• Respiratory alkalosis.

Diagnostic Evaluation

• Troponin :– Serum troponin I and troponin T are elevated in 30

to 50 percent of patients who have a moderate to large pulmonary embolism.

– Presumed mechanism is acute right heart overload.

• Brain Naturetic Peptide:– Very non specific peptide – Large elevation can suggest poor prognosis

Diagnostic Evaluation

• Electrocardiogram– ECG abnormalities common in patients with and

without PE – limiting the diagnostic usefulness of the ECG– Most common Ekg finding is a sinus tachycardia

• Or non specific ST and T wave changes

– abnormalities historically considered to be suggestive of PE

• S1Q3T3 pattern, right ventricular strain, new incomplete right bundle branch block

Diagnostic Evaluation

• V/Q scan :– The most extensive evaluation of the accuracy of

the ventilation-perfusion (V/Q) scan was the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED)

– Accuracy was based on comparison with the gold standard test of Pulmonary angiogram

– The found clincally accuracy was best when combined with pretest probabilities

Diagnostic Evaluation

• V/Q scan :• Patients with high clinical probability of PE and

a high-probability V/Q scan had a 95 percent likelihood of having PE

• Patients with low clinical probability of PE and a low-probability V/Q scan had only a 4 percent likelihood of having PE

• A normal V/Q scan virtually excluded PE

Diagnostic Evaluation

• Ultrasound:– In some patients clinicians have attempted to use

lower extremity Doppler's to evaluate– Studies show that many patients with PE are

missed– Bilateral lower extremity doppler’s will decrease

the rate of missed DVT – Operator dependent

Diagnostic Evaluation

• D-dimer:– D-dimer is a degradation product of cross-linked fibrin. It can

be detected in serum using a variety of different assays:– Enzyme-linked immunosorbent assay (ELISA) (results in >8 hrs)– Quantitative rapid ELISA (results in 30 min)– Semi-quantitative rapid ELISA (results in 10 min)– Qualitative rapid ELISA (results in 10 min)– Quantitative latex agglutination assay (results in 10 to 15 min)– Semi-quantitative latex agglutination assay (results in 5 min)

Diagnostic Evaluation

• D-Dimer:• For the quantitative assays, a level >500

ng/mL is usually considered abnormal • They are best characterized as having good

sensitivity and negative predictive value• Poor specificity and positive predictive value.

Diagnostic Evaluation

• Angiography :– Pulmonary angiography is the definitive diagnostic

technique or "gold standard" in the diagnosis of acute PE.

– It is performed by injecting contrast into a pulmonary artery branch after percutaneous catheterization, usually via the femoral vein. A filling defect or abrupt cutoff of a small vessel is indicative of PE.

Diagnostic Evaluation

• Angiography:– A negative pulmonary angiogram excludes

clinically relevant PE.– Pulmonary angiography is generally safe and well

tolerated in the absence of hemodynamic instability caused by acute, severe pulmonary hypertension

– Radiation exposure depends on the length and complexity of the procedure, and greater than CT.

Source Undetermined

Diagnostic Evaluation

• Spiral CT:– Spiral (helical) CT scanning with intravenous

contrast ( CT pulmonary angiography or CT-PA) is being used increasingly as a diagnostic modality for patients with suspected PE

– Initial reports suggested that 98 percent of patients with PE were detected by CT-PA; however, that value decreased to 53 to 87 percent in subsequent studies

Source Undetermined

Source Undetermined

Source Undetermined

Source Undetermined

PERC

• The following eight factors constitute the PE rule-out criteria (PERC):

• Age less than 50 years• Heart rate less than 100 bpm• Oxyhemoglobin saturation ≥95 percent• No hemoptysis• No estrogen use• No prior DVT or PE• No unilateral leg swelling• No surgery or trauma requiring hospitalization within the

past four weeks